全文获取类型
收费全文 | 460篇 |
免费 | 30篇 |
专业分类
林业 | 8篇 |
农学 | 22篇 |
基础科学 | 3篇 |
56篇 | |
综合类 | 46篇 |
农作物 | 22篇 |
水产渔业 | 35篇 |
畜牧兽医 | 263篇 |
园艺 | 2篇 |
植物保护 | 33篇 |
出版年
2023年 | 5篇 |
2020年 | 11篇 |
2019年 | 14篇 |
2018年 | 11篇 |
2017年 | 6篇 |
2016年 | 16篇 |
2015年 | 6篇 |
2014年 | 8篇 |
2013年 | 24篇 |
2012年 | 11篇 |
2011年 | 23篇 |
2009年 | 10篇 |
2008年 | 22篇 |
2007年 | 21篇 |
2006年 | 15篇 |
2005年 | 18篇 |
2004年 | 15篇 |
2003年 | 15篇 |
2002年 | 13篇 |
2001年 | 15篇 |
2000年 | 11篇 |
1999年 | 14篇 |
1998年 | 4篇 |
1997年 | 4篇 |
1993年 | 3篇 |
1992年 | 6篇 |
1991年 | 7篇 |
1990年 | 11篇 |
1989年 | 5篇 |
1988年 | 7篇 |
1987年 | 7篇 |
1986年 | 8篇 |
1985年 | 7篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1977年 | 5篇 |
1976年 | 7篇 |
1975年 | 8篇 |
1974年 | 6篇 |
1973年 | 10篇 |
1972年 | 7篇 |
1971年 | 6篇 |
1970年 | 8篇 |
1969年 | 7篇 |
1968年 | 4篇 |
1967年 | 5篇 |
排序方式: 共有490条查询结果,搜索用时 0 毫秒
1.
Serum antibody (virus neutralisation, complement fixation, IgM and IgG) responses to equine herpesvirus-1 (EHV-1) infection were measured in six foals which were initially free from EHV-1 and EHV-4 infection and maternally-derived antibodies. Following primary infection, high titres of virus neutralisation and complement fixation antibodies were detectable against EHV-1, however, corresponding antibody levels against EHV-4 were low or inapparent, although the two viruses share a number of cross-reactive epitopes. In addition, following the primary infection with EHV-1, IgM levels increased before those of IgG, virus neutralisation and complement fixation antibodies, peaked sooner and thereafter declined. Stimulation of IgM levels was observed on secondary infection with EHV-1 given 61 days later. In contrast, IgG, virus neutralisation and complement fixation antibodies following primary infection were more sustained and no increase in their levels was observed on secondary infection. No consistent changes in IgM or IgG levels were seen after administration of dexamethasone to reactivate latent virus. 相似文献
2.
Five Devon cattle with suspected ceroid-lipofuscinosis and aged between 19 and 39 months of age were humanely slaughtered and subjected to post-mortem examination. There was severe atrophy of the cerebrum, particularly of the occipital cortex. Microscopy also showed severe atrophy of the retina with complete loss of photoreceptor cells, even in the youngest animal examined. Histopathologically the disease was characterised by accumulation of a fluorescent lipopigment in neurones, including those of the retina and a severe astrocytosis. The disease, which is characterised by the accumulation of subunit c of mitochondrial ATP synthase, is similar to that extensively described in South Hampshire sheep except that the retinal lesions were more severe. In contrast, tremors were not noted in the cattle. The clinical history and similarity to the disease in sheep and other species indicated inheritance was as an autosomal recessive trait. 相似文献
3.
A new syndrome, characterised by acute respiratory distress and by abnormalities of the skin, hair and thyroid, was the apparent cause of neonatal death in 35 (24 per cent) of 146 piglets sired by a large white boar in four small commercial pig units. The syndrome appears to be of genetic origin, inherited as an autosomal recessive trait. Its similarities with the respiratory distress syndrome (RDS) of the newborn infant and the "barker" syndrome of the newborn foal are discussed. 相似文献
4.
5.
Shoot dry weight, leaf area, leaf lamina dry weight and N-fixation of L. uliginosus cv. Grasslands 4705 were compared with those of T. repens S184 over a 90-day period frotn sowing, in pots in a greenhouse. Three P and three pH levels were imposed and there were three destructive harvests at 30-day intervals. N-fixation was estimated by the acetylene reduction technique prior to the last harvest. L. uliginosus had higjier means than T. repens for all characters measured under all treatments at all harvests. Large increases in shoot weight and leaf area were associated with addition of P, particularly with the first increment of P to L. uliginosus. High P reduced the contribution of lamina to total shoot weight in T. repens more than in L. uliginosus at the second harvest. Raising pH increased shoot weight and leaf area in both species. N-fixation was low in both species at low pH and low P. This was increased by addition of P, a smaller quantity being necessary for the same response in L. uliginosus compared with T. repens. At the higher P levels, the high pH gave rise to lower N-fixation than at the medium pH. Results are discussed in relation to field trials of other workers and the possible suitability of L. uliginosus for low fertility upland conditions. 相似文献
6.
Some behavioural and ecological factors affecting distribution,biomass and production of juvenile Atlantic salmon 下载免费PDF全文
R. John Gibson 《Ecology of Freshwater Fish》2015,24(3):397-411
Observations were made in an experimental stream tank (total area 14.7 m2) on juvenile Atlantic salmon, Salmo salar L (parr), relating experimental observations to field observations, including the reported diurnal fasting behaviour of juvenile salmon at water temperatures <10 °C. Densities in the tank ranged from five to twenty parr, at water temperatures ranging from 4.6 °C to 15.8 °C. The wide channel of the stream tank, with mean water velocity of 18.8 cm·s?1, was the preferred section, where territorial behaviour was observed. Biomass was regulated in the wide channel by territorial mosaics or by dominance hierarchies. Dominance hierarchies were reflected in coloration of the fish. Dominant salmon were generally in the wide channel. Densities of salmon parr (of mean fork length 10.2 cm) in the channel ranged from 0.84 m?2 to 1.73 m?2, with an average biomass of 14.2 g·m?2. Growth was least at the 5.9 °C temperature treatment. In experiments at temperatures below 10 °C, feeding, dominance hierarchy and territorial behaviour were observed in daylight hours, contrary to the published literature. Interactions with other species may affect behaviour. Some observations were made on a closely related species, brown trout (Salmo trutta L.), a commonly cohabiting species in many systems. Trout displaced salmon from their preferred locations in the tank and were more aggressive than the salmon, reducing agonistic behaviour by the salmon. The commonest agonistic act shown by salmon was ‘charge’ and that by the trout was ‘approach’. Some field observations affecting behaviour and production are discussed. 相似文献
7.
8.
Maes D Gibson K Trigo E Saszak A Grass J Carlson A Blaha T 《Berliner und Münchener tier?rztliche Wochenschrift》2001,114(9-10):339-341
This field study investigated the efficacy of a Salmonella Choleraesuis live vaccine (Argus SC) to reduce the number of infections with Salmonella. Twelve groups of about 380 pigs each were randomly allocated to either vaccination (V) or no vaccination (C). The vaccine was applied orally at 3 and 16 weeks. Forty pigs per group were blood sampled at 3, 10, 16, and 24 weeks to detect possible antibodies against Salmonella. The prevalence of Salmonella in the lymph nodes was the major variable. In the V groups, only 0.6% of the lymph nodes were positive, whereas 7.2% were positive in the C groups (p < 0.001). The percentage of seropositive pigs at 24 weeks (cut-off OD > 10) was 26% and 9% in the V and C groups, respectively (p < 0.001). The present study documented that vaccination with a live modified S. Choleraesuis vaccine is a useful tool to lower the prevalence of Salmonella in swine herds. 相似文献
9.
10.